To obtain information on the relationship between dust mites exposure, dust mite sensitization, and the development of extrinsic asthma in Jiangsu province between 1992-1993, a case-control study was carried out. Unconditional logistic regression method was conducted. The results showed that the history of allergy in parents, dust mites exposure, dust mite sensitization, and birth in months with high mite densities were factors which played important roles in the development of extrinsic asthma. The population attributable rate of dust mites exposure was 70.29%. Based on the results, some practical preventive measures were put forward.